when pushback function of std::vector make program crash? How to handle it?

[Qt embedded developer]

Hi have faced one issue when my application get crash due to below line:

strVehicleNo = "abc";

VecVehicleCodeDigit.push_back(strVehicleNo.substr(strVehicleNo.length() - 4));

i want to find generic solution for this problem.

[JoeCFD]

if ( strVehicleNo.length()  > 4 ) {
    VecVehicleCodeDigit.push_back(strVehicleNo.substr(strVehicleNo.length() - 4));
}
else {
    std::cout << " string " << strVehicleNo << " is ignored" <<std::endl;
}

[JonB]

@Qt-embedded-developer

• Check your VecVehicleCodeDigit.
• strVehicleNo.substr(strVehicleNo.length() - 4): given that you can see your string is 3 characters long, what do you expect from this? Strange question....

[JoeCFD]

if ( strVehicleNo.length()  > 4 ) {
    VecVehicleCodeDigit.push_back(strVehicleNo.substr(strVehicleNo.length() - 4));
}
else {
    std::cout << " string " << strVehicleNo << " is ignored" <<std::endl;
}

[Qt embedded developer]

@JoeCFD i want to know pushback function why make program crash. Is it unauthorized memory access problem?

[Qt embedded developer]

@JonB hi this data come from server and it need to be like "GJ-05-4578". But when server data wrong come like " M3". Then this crash happen.

[JonB]

@Qt-embedded-developer
Did you read what I wrote and actually think about it?

strVehicleNo.substr(strVehicleNo.length() - 4): given that you can see your string is 3 characters long, what do you expect from this?

Obviously M3 is even shorter. So you cannot subtract 4 from its length, can you?

But when server data wrong come like " M3". Then this crash happen.

Either sort out why "wrong data" can come from server, or code to allow for it so your client does not crash.

I really do not understand what your actual question is or what you expect people to say about it.

[Qt embedded developer]

@JonB i want to know pushback function why make program crash. Is it unauthorized memory access problem?

[SGaist]

Hi,

@Qt-embedded-developer did you actually to do the math that @JonB suggested ?

It's not the push_back call that is the issue, it's your substr call.

Use a debugger.

[Qt embedded developer]

Thank you all dear for answers...